Electronic device assemblies and vehicles employing dual phase change materials

ABSTRACT

Electronic device assemblies employing dual phase change materials and vehicles incorporating the same are disclosed. In one embodiment, an electronic device assembly includes a semiconductor device having a surface, wherein the semiconductor device operates in a transient heat flux state and a normal heat flux state, a coolant fluid thermally coupled to the surface of the semiconductor device, and a phase change material thermally coupled to the surface of the semiconductor device. The phase change material has a phase change temperature at which the phase change material changes from a first phase to a second phase. The phase change material absorbs heat flux at least when the semiconductor device operates in the transient heat flux state.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/561,229,filed on Jul. 30, 2012.

TECHNICAL FIELD

The present specification generally relates to electronic deviceassemblies and, more particularly, to electronic device assemblieshaving a cooling system that employs dual phase change materials toremove thermal flux.

BACKGROUND

Heat transfer devices may be coupled to a heat generating device, suchas a semiconductor device, to remove heat and lower the maximumoperating temperature of the heat generating device. Cooling fluid maybe used in heat transfer devices to receive heat generated by the heatgenerating device by convective thermal transfer, and remove such heatfrom the heat generating device. Other heat transfer devices may removethermal energy by two-phase heat transfer, wherein coolant fluid isconverted from a liquid phase to a gas phase at the location of thermalflux.

Semiconductor devices, such as power semiconductor devices, aretypically exposed to both transient and steady-state heat loads. In thetransient heat load distribution, the heat flux reaches a high peakvalue for a short period of time, and then drops to a lower steady statevalue. However, the design of the cooling system for the electronicdevice assembly should be such that it can meet both the transient andsteady-state heat loads. Designing the cooling system to meet thetransient load requirement may result in a system that iscost-prohibitive, oversized, and heavy.

Accordingly, a need exists for alternative cooling systems forelectronic device assemblies.

SUMMARY

In one embodiment, an electronic device assembly includes asemiconductor device having a surface, wherein the semiconductor deviceoperates in a transient heat flux state and a normal heat flux state, acoolant fluid thermally coupled to the surface of the semiconductordevice, and a phase change material thermally coupled to the surface ofthe semiconductor device. The phase change material has a phase changetemperature at which the phase change material changes from a firstphase to a second phase. The phase change material absorbs heat flux atleast when the semiconductor device operates in the transient heat fluxstate.

In another embodiment, an electronic device assembly includes asemiconductor device, a coolant fluid, one or more thermally conductivefeatures, and a phase change material disposed within the one or morethermally conductive features. The semiconductor device includes asurface, and operates in a transient heat flux state and a normal heatflux state. The coolant fluid is thermally coupled to the surface of thesemiconductor device, and has a fluid phase change temperature at whichthe coolant fluid changes to a vapor. The coolant fluid changes to avapor when the semiconductor device operates at the normal heat fluxstate or the transient heat flux state. The one or more thermallyconductive features are thermally coupled to the surface of thesemiconductor device. Each thermally conductive feature of the one ormore thermally conductive features defines an enclosure in which thephase change material is disposed. The phase change material has a phasechange temperature at which the phase change material changes from asolid to a liquid.

In yet another embodiment, a vehicle includes an electric motor and apower electronics module having an electronic device assembly. The powerelectronics module is electrically coupled to the electric motor, andincludes a semiconductor device having a surface, a coolant fluidthermally coupled to the surface of the semiconductor device, and aphase change material also thermally coupled to the surface of thesemiconductor device. The semiconductor device operates in a transientheat flux state and a normal heat flux state. The phase change materialhas a phase change temperature at which the phase change materialchanges from a first phase to a second phase. The phase change materialabsorbs heat flux at least when the semiconductor device operates in thetransient heat flux state.

These and additional features provided by the embodiments describedherein will be more fully understood in view of the following detaileddescription, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1A schematically depicts an exemplary electronic device assemblyhaving dual phase change materials according to one or more embodimentsdescribed and illustrated herein;

FIG. 1B schematically depicts an exemplary electronic device assemblyhaving a cold plate and dual phase change materials according to one ormore embodiments described and illustrated herein;

FIG. 2A schematically depicts an elevation view of an exemplaryelectronic device assembly having dual phase change materials accordingto one or more embodiments described and illustrated herein;

FIG. 2B schematically depicts a top view of the exemplary electronicdevice assembly depicted in FIG. 2A;

FIG. 2C schematically depicts a perspective view of the exemplaryelectronic device assembly depicted in FIG. 2A without the jetimpingement nozzle;

FIG. 3 schematically depicts a top view of an exemplary electronicdevice assembly having a plurality of radially extending, thermallyconductive features containing a phase change material according to oneor more embodiments described and illustrated herein;

FIG. 4A schematically depicts an internal elevation view of an exemplaryelectronic device assembly having a plurality of free moving, thermallyconductive features containing a phase change material according to oneor more embodiments described and illustrated herein;

FIG. 4B schematically depicts an internal top view of the exemplaryelectronic device assembly depicted in FIG. 4A;

FIG. 5 schematically depicts a perspective view of a power electronicsmodule having a plurality of electronic device assemblies according toone or more embodiments described and illustrated herein; and

FIG. 6 schematically depicts a perspective view of a vehicle includingan electric motor and a power electronics module having a plurality ofelectronic device assemblies according to one or more embodimentsdescribed and illustrated herein.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to electronic deviceassemblies that utilize dual phase change materials to cool asemiconductor device that operates at different heat flux states. Forexample, the semiconductor device may operate in a transient heat fluxstate caused by a temporary increase in current passing through thesemiconductor device (e.g., initial application of a load to thesemiconductor device). The semiconductor device may also operate in anormal heat flux state that corresponds with a steady state operation(e.g., normal, steady state operation of the semiconductor device). Theheat flux caused by the transient heat flux state is greater than theheat flux caused by the normal heat flux state. As an example and not alimitation, the transient heat load distribution during the transientheat load state may reach a peak value of approximately 200 W/cm² for afraction of a second, and then fall to a lower steady-state value ofapproximately 100 W/cm² during the normal heat flux state.

Generally, embodiments utilize a second phase change material as anenergy storage device that supplements a main, first phase changematerial in a dual phase change material system. The second phase changematerial is configured and placed with respect to a semiconductor deviceto store energy created by the semiconductor device when it operates inthe transient heat flux state. The first phase change material, which insome embodiments is a liquid that impinges a surface of thesemiconductor device (active cooling), has a phase change temperaturethat is greater than a phase change temperature of the second phasechange material to cool the semiconductor device during the normal heatflux state. In this manner, embodiments utilize dual phase changematerials to effectively cool the semiconductor device during bothtransient and steady state operations. Various embodiments of electronicdevices assemblies having dual phase change materials and vehiclesincorporating the same are described in detail below.

Referring now to FIG. 1A, an electronic device assembly 100 according toone embodiment is schematically depicted. The electronic device assembly100 generally comprises a semiconductor device 110 (or other heatgenerating component) having a surface 112, a first phase changematerial 120 and a second phase change material 130. The semiconductordevice 110 may be configured as a power semiconductor device deployed ina high power application. As an example and not a limitation, thesemiconductor device 110 may be included in a power electronic module asa component in an inverter and/or converter circuit used to electricallypower high load devices, such as electric motors in electrified vehicles(e.g., hybrid vehicles, plug in hybrid electric vehicles, plug inelectric vehicles, and the like). It should be understood that theelectronic device assembly 100 may be used in applications other thanvehicular applications (e.g., power transmission, machinery,construction equipment, and the like).

Although the semiconductor device 110 is depicted as an insulated gatebipolar transistor (IGBT), the semiconductor device 110 may beconfigured as any semiconductor device including, but not limited to,MOSFETs, power diodes, power bipolar transistors, and power thyristordevices. The cooling techniques of the embodiments of the presentdisclosure may also be utilized to cool heat generating devices otherthan semiconductor devices, such as motors or other mechanicalequipment, for example.

The electronic device assembly 100 further comprises a first phasechange material 120 and a second phase change material 130 that arethermally coupled to one or more surfaces (e.g., surface 112) of thesemiconductor device 110. The first and second phase change materials120, 130 are configured to change phases at particular temperatures tostore thermal energy and remove it from the semiconductor device. Asdescribed above, the semiconductor device 110 may operate at a transientheat flux state of high heat flux distribution and a normal heat fluxstate having a heat flux distribution lower than that of the transientheat flux state. The first phase change material 120 may be configuredas a liquid that changes to a vapor at a first phase change temperature.The second phase change material 130 may be configured as a solid thatchanges to a liquid at a second phase change temperature. As describedbelow, some embodiments utilize the first, liquid phase change materialfor jet impingement. In such embodiments, the first phase changematerial may not change to a vapor.

In one embodiment, the first phase change material 120 is a coolantfluid (i.e., a liquid) that is fluidly coupled to the surface 112 of thesemiconductor device 110. Examples of the coolant fluid include, but arenot limited to, deionized water and engineered fluids, such as HFE-7100.As described in more detail below, the coolant fluid may be provided ina closed system, or in a coolant fluid system wherein the coolant fluidis cycled to and from a coolant fluid reservoir. The second phase changematerial 130 may be a solid that is thermally coupled to the surface 112of the semiconductor device 110. The second phase change material 130may have a phase change temperature that is lower than that of the firstphase change material 120, and is configured to change phases from asolid to a liquid when the second phase change temperature is reached.The second phase change material 130 stores the high thermal energygenerated by the transient load operation of the semiconductor device110. The second phase change material 130 may be configured as anymaterial having a phase change temperature that may absorb heat fluxgenerated by operation of the semiconductor device during the transientheat flux state. As an example and not a limitation, the second phasechange material 130 may be configured as an energy storage material suchas paraffin wax.

In this manner, the transient spikes in the heat load may be absorbedefficiently due to the phase change of the second phase change material,which in turn keeps the semiconductor device 110 temperature at aconstant value. While at lower steady state heat loads, the first phasechange material may adequately cool the semiconductor device 110 (eitherby convection, jet impingement, or phase change). Such a dual phasechange material approach may lower the overall cost and weight of thecooling system of the electronic device assembly. In some embodiments,particularly embodiments wherein the first phase change material isconfigured as a coolant fluid that impinges the semiconductor device,the first phase change material may not change to a vapor but ratherabsorb the thermal energy and remove it by flowing away from thesemiconductor device. In other embodiments, the first phase changematerial removes thermal energy both by jet impingement and phasechange.

Referring now to FIG. 1B, an alternative electronic device assembly 100′having an intermediate cold plate 170 positioned between thesemiconductor device 110 and the first and second phase change materials120, 130 is illustrated. The cold plate 170 may be made of a thermallyconductive material, examples of which include, but are not limited to,copper, aluminum, and thermally conductive polymers. The semiconductordevice 110 may be thermally coupled to a heated surface 172 of the coldplate 170 by any coupling technique, such as by soldering, brazing, andthe like. One or more intermediary bonding layers may be present betweenthe surface 112 of the semiconductor device 110 and the heated surface172 of the cold plate 170. The first and second phase change material120, 130 may then be thermally coupled to a cooling surface 174 of thecold plate 170.

It should be understood that any of the embodiments described herein mayinclude such an intermediary cold plate even if it is not illustrated ina particular figure. Restated, the cold plate 170 is an optionalcomponent that may or may not be included in the electronic deviceassembly.

Referring now to FIGS. 2A-2C, an exemplary electronic device assembly200 according to one embodiment is illustrated. FIG. 2A is an elevationview, FIG. 2B is a top view, and FIG. 2C is a perspective view of theelectronic device assembly 200. The exemplary electronic device assembly200 is configured as a jet impingement, active cooling system whereinthe first phase change material is configured as a coolant fluid 220that impinges a region 215 of the surface 212 of the semiconductordevice 210. The electronic device assembly 200 depicted in FIG. 2Aincludes a jet impingement nozzle 240 that is fluidly coupled to a fluidline 250. In one embodiment, the fluid line 250 is fluidly coupled to afluid reservoir (not shown) where it is cooled prior to flowing throughthe jet impingement nozzle 240. It is noted that the jet impingementnozzle 240 and fluid line 250 are not shown in FIG. 2C for ease ofillustration.

The jet impingement nozzle 240 is configured to form a jet of coolantfluid 220 that impinges the surface 212 of the semiconductor device 210at a region 215 having a high thermal flux distribution. In some cases,the region 215 may be a central region of the surface 212. The coolantfluid 220 strikes the surface 212 of the semiconductor device 210 whereit absorbs the thermal energy generated by the semiconductor device 210.Some of the coolant fluid 220 may change from a liquid to a vapor uponcontacting the surface 212, thereby cooling the semiconductor device 210during the normal heat flux state. The coolant fluid vapor and excesscoolant fluid 220 may then pass through an outlet (not shown) to becooled and then recycled back through the jet impingement nozzle 240.Additionally, the electronic device assembly 200 further includes ahousing (not shown) to maintain the coolant fluid 220 within theelectronic device assembly 200.

In the illustrated embodiment, the electronic device assembly 200further includes a first thermally conductive feature 232 a and a secondthermally conductive feature 232 b that are located at a first edge 211and a second edge 213 of the semiconductor device 210, respectively. Thefirst and second thermally conductive features 232 a, 232 b may bethermally coupled to the surface by a variety of techniques, such as bysoldering or brazing, for example. As stated above, a cold plate may becoupled to the surface 212 of the semiconductor device 210 such that thefirst and second thermally conductive features 232 a, 232 b arethermally coupled to the cold plate.

The first and second thermally conductive features 232 a, 232 b defineenclosures in which the second phase change material 230 is encased. Thefirst and second thermally conductive features 232 a, 232 b may be madeof a thermally conductive material, such as, but not limited to, copper,aluminum, and thermally conductive polymers. The first and secondthermally conductive features 232 a, 232 b are configured to maintainthe second phase change material 230 in close proximity to the surface212 of the semiconductor device 210 so that it may receive the transientheat flux load. Although the second phase change material 230 is shownon a bottom region of an enclosure 233 defined by the first and secondthermally conductive features 232 a, 232 b, the second phase changematerial 230 may also be adhered to the top and sidewalls of the firstand second thermally conductive features 232 a, 232 b in actualpractice.

When the semiconductor device 210 operates in the normal heat flux stateor the transient heat flux state, the temperature of the surface 212increases to at or above the phase change temperature of the secondphase change material 230. The second phase change material 230 absorbsthe transient heat flux and changes from a solid to a liquid, and storesthe thermal energy generated by the semiconductor device 210 duringtransient load operation. The liquid of the second phase change material230 is maintained within the first and second thermally conductivefeatures 232 a, 232 b. The coolant fluid 220 continues to cool thesemiconductor device 210 during the normal heat flux state operation.

In an alternative embodiment, the first phase material 220 is notimpinged on the surface 212 of the semiconductor device 210, but ratheris pooled between the first and second thermally conductive features 232a, 232 b such that the coolant fluid 220 experiences pool boiling duringthe transient or normal heat flux operating states (i.e., passivecooling rather than active cooling provided by jet impingement).

It should be understood that any number of thermally conductive featuresmay be provided in any number of configurations. The number andarrangement of the thermally conductive features and the encased secondphase change material may depend on the particular type of semiconductordevice and application, and therefore the thermal load distribution onthe surface of the semiconductor device. The second phase changematerial may be strategically located on the surface of thesemiconductor device to absorb any transient heat loads withoutviolating the maximum operating temperature of the semiconductor device.

Referring now to FIG. 3, another exemplary electronic device assembly300 is schematically depicted. In this embodiment, the thermallyconductive features are configured as a plurality of radially arranged,thermally conductive features 332 a-332 g that is thermally coupled tothe surface 312 of the semiconductor device 310. The radially arranged,thermally conductive features 332 a-332 g may be made of a thermallyconductive material, such as, but not limited to, copper, aluminum, andthermally conductive polymers. In the illustrated embodiment, eachradially arranged, thermally conductive feature 332 a-332 g extends froman edge of the surface 312 toward the center. The radially arranged,thermally conductive features 332 a-332 g terminate at a central region315 of the surface 312. As described above with respect to FIGS. 2A-2C,the electronic device assembly 300 may further include a jet impingementnozzle 340 that causes coolant fluid 320 to impinge the central region315 (or other region) of the surface 312 of the semiconductor device310. Any number of thermally conductive features 332 a-332 g may beutilized. Additionally, each of thermally conductive features 332 a-332g may also include additional branches, such as in a heat sink-likeconfiguration.

As described above with respect to FIG. 2, the second phase changematerial is encased within each radially arranged, thermally conductivefeature 332 a-332 g. It is noted that the second phase change materialis not visible in FIG. 3. As the surface 312 of the semiconductor devicereaches the phase change temperature of the second phase changematerial, the second phase change material changes from a solid to aliquid, and stores thermal energy generated during the transient heatflux state.

In the illustrated embodiment, the first phase change material isconfigured as a coolant fluid 320 as described above with respect to theembodiment depicted in FIG. 2. The coolant fluid 320 may be directedtoward the central region 315 (or other region) of the surface 312 ofthe semiconductor device 310 by a jet impingement nozzle 340. Afterimpinging the surface 312, the coolant fluid 320 may be directedradially outward, where it may pass by the radially arranged, thermallyconductive features 332 a-332 g, as well as transition from a liquid toa vapor. The coolant fluid 320 may be maintained within the electronicdevice assembly 300 by a housing (not shown), and removed by an outletand/or condenser unit (not shown).

The active cooling provided by the coolant fluid 320 cools thesemiconductor device 310 during the normal heat flux state (i.e., steadystate operation), and the passive cooling provided by the second phasechange material cools the semiconductor device during the transient heatflux state.

Embodiments may also be configured such that the first phase changematerial provides passive rather than active cooling. The first phasechange material may be provided in a closed system such that cooling isprovided by pool boiling rather than jet impingement. For example,referring to the embodiments depicted in FIGS. 2 and 3, the electricaldevice assembly may not include a jet impingement nozzle, but rather thecoolant fluid may be enclosed in a housing and thermally coupled to thesurface of the semiconductor device for pool boiling heat transfer.

FIGS. 4A and 4B schematically depict an exemplary electronic deviceassembly 400 that utilizes passive cooling for both the first phasechange material and the second phase change material. The exemplaryelectronic device assembly 400 generally comprises a housing 460 that,along with a surface 412 of a semiconductor device 410, defines anenclosure 462 in which the first phase change material is maintained.The first phase change material is configured as a coolant fluid 420 asdescribed above with respect to FIG. 2. The coolant fluid 420 is fluidlycoupled to the surface 412 of the semiconductor device 410 to receiveheat flux generated by the semiconductor device 410.

The electronic device assembly 400 further comprises one or more freelymoving, thermally conductive features 432 disposed in the coolant fluid420 within the enclosure 462. The freely moving, thermally conductivefeatures 432 are not rigidly coupled to the surface 412 of thesemiconductor device 410 (or any intermediate cold plate), and are freeto move within the enclosure 462. Each freely-moving, thermallyconductive feature 432 defines an enclosure in which second phase changematerial is encased. The second phase change material may be configuredas described above with respect to FIGS. 2 and 3. It is noted that thesecond phase change material is not visible in FIGS. 4A and 4B.

The freely moving, thermally conductive features 432 may be made of athermally conductive material, such as, but not limited to, copper,aluminum, and thermally conductive polymers. In the illustratedembodiment, the freely moving, thermally conductive features 432 areconfigured as spheres in which the second phase change material isdisposed. However, the freely moving, thermally conductive features 432may possess shapes other than spheres. Further, the freely moving,thermally conductive features 432 may have different sizes as depictedin FIGS. 4A and 4B, or they may all have the same size.

When the semiconductor device 410 operates in one or more states suchthat the temperature of the surface 412 rises to at or above the phasechange temperature of the second phase change material, the second phasechange material to changes from a solid to a liquid. Additionally, thetransient heat flux state and/or the normal heat flux state causes thecoolant fluid 420 to boil and change to a vapor. The presence of thefreely moving, thermally conductive features 432 within the coolantfluid 420 further facilitates pool boiling of the coolant fluid 420 asthey accept the heat flux from the semiconductor device and provideadditional nucleation sites.

A plurality of electronic device assemblies as described above may beprovided in a power electronics module to create a larger powerelectronics circuit. FIG. 5 depicts an exemplary power electronicsmodule 500 comprising a plurality of electronic device assemblies 505a-505 h. The electronic device assemblies 505 a-505 h each include afirst phase change material and a second phase change material to coolone or more semiconductor devices during at least two heat flux states.In the illustrated embodiment, the plurality of electronic deviceassemblies 505 a-505 h is coupled to a thermally conductive substrate502. In some embodiments, particularly, those using active cooling witha coolant fluid as the first phase change material, the powerelectronics module 500 may further include coolant fluid inlet andoutlet manifolds (not shown) to provide and remove coolant fluid to andfrom the power electronics module 500.

As stated above, the electronic device assemblies described herein maybe incorporated into larger power circuits, such as inverter and/orconverter circuits of an electrified vehicle. The electrified vehiclemay be a hybrid vehicle, a plug-in electric hybrid vehicle, an electricvehicle, or any vehicle that utilizes an electric motor. Referring nowto FIG. 6, a vehicle 600 configured as a hybrid vehicle or a plug-inhybrid vehicle is schematically illustrated. The vehicle generallycomprises a gasoline engine 670 and an electric motor 672, both of whichare configured to provide rotational movement to the wheels 680 of thevehicle 600 to propel the vehicle 600 down the road. A power circuit 602is electrically coupled to electric motor 672 (e.g., by conductors 678).The power circuit 602 may be configured as an inverter and/or aconverter circuit that provides electrical power to the electric motor672. The power circuit 602 may in turn be electrically coupled to apower source, such as a battery pack 674 (e.g., by conductors 676). Thepower circuit 602 includes one or more power electronics modules 605(see FIG. 5) that include one or more electronic device assemblies. Theone or more electronic device assemblies comprise the first phase changematerial and the second phase change material, as described above. Whenthe semiconductor devices of the one or more power electronics modules605 operates in one or more of the heat flux states, the second phasechange material changes from a solid to a liquid.

It should now be understood that embodiments of the present disclosureare directed to electronic device assemblies employing dual phase changematerials to adequately cool a semiconductor device during both normalheat load distributions and transient heat load distributions withoutover designing the cooling system to accommodate the greatertemperatures of the transient heat load distributions. A second phasechange material is used as an energy storage device that supplements amain, first phase change material during transient spikes in the heatload during transient operation of the semiconductor device. The secondphase change material is efficiently absorbed due to the second phasechange material. During normal, steady-state operation, the phase changeof the first phase change material, which may be deployed in an activeor passive cooling arrangement, cools the semiconductor device.

It is noted that the term “approximately” may be utilized herein torepresent the inherent degree of uncertainty that may be attributed toany quantitative comparison, value, measurement, or otherrepresentation. Such terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

While particular embodiments have been illustrated and described herein,it should be understood that various other changes and modifications maybe made without departing from the spirit and scope of the claimedsubject matter. Moreover, although various aspects of the claimedsubject matter have been described herein, such aspects need not beutilized in combination. It is therefore intended that the appendedclaims cover all such changes and modifications that are within thescope of the claimed subject matter.

What is claimed is:
 1. A cooling system comprising: a cold platecomprising a cooling surface; a housing coupled to the cooling surfaceof the cold plate and defining an enclosure to receive a coolant fluid;one or more thermally conductive features thermally coupled to thecooling surface of the cold plate; and a phase change material disposedwithin the one or more thermally conductive features, the phase changematerial thermally coupled to the cooling surface of the cold plate,wherein the phase change material has a phase change temperature atwhich the phase change material changes from a first phase to a secondphase.
 2. The cooling system of claim 1, wherein the phase changematerial is a solid when it is at a temperature below the phase changetemperature.
 3. The cooling system of claim 1, wherein at least one ofthe one or more thermally conductive features is physically connected tothe cooling surface of the cold plate.
 4. The cooling system of claim 1,wherein at least one of the one or more thermally conductive features isnot physically coupled to the cooling surface of the cold plate.
 5. Thecooling system of claim 1, wherein the one or more thermally conductivefeatures are located at one or more edges of the cooling surface of thecold plate.
 6. The cooling system of claim 1, wherein the one or morethermally conductive features comprises a plurality of radially arrangedthermally conductive features.
 7. The cooling system of claim 1, whereinat least one of the one or more thermally conductive features is asphere that is not physically connected to the cooling surface of thecold plate.
 8. The cooling system of claim 1, wherein the phase changematerial comprises paraffin wax.
 9. The cooling system of claim 1,further comprising a jet impingement nozzle configured to direct thecoolant fluid toward the cooling surface of the cold plate.
 10. Thecooling system of claim 1, wherein the coolant fluid has a fluid phasechange temperature that is lower than the phase change temperature ofthe phase change material.
 11. A power electronics module comprising: athermally conductive substrate; a plurality of electronic deviceassemblies thermally coupled to the thermally conductive substrate, eachelectronic device assembly of the plurality of electronic deviceassemblies comprising: a semiconductor device comprising a surface; ahousing configured to receive a coolant fluid thermally coupled to thesurface of the semiconductor device; one or more thermally conductivefeatures thermally coupled to the surface of the semiconductor deviceand disposed within the housing; and a phase change material disposedwithin the one or more thermally conductive features, the phase changematerial thermally coupled to the surface of the semiconductor device,wherein the phase change material has a phase change temperature atwhich the phase change material changes from a first phase to a secondphase.
 12. The power electronics module of claim 11, wherein: thesemiconductor device operates in a transient heat flux state and anormal heat flux state; and the phase change material absorbs heat fluxat least when the semiconductor device operates in the transient heatflux state.
 13. The power electronics module of claim 11, wherein thephase change material is a solid when it is at a temperature below thephase change temperature.
 14. The power electronics module of claim 11,wherein at least one of the one or more thermally conductive features isphysically connected to the surface of the semiconductor device.
 15. Thepower electronics module of claim 11, wherein at least one of the one ormore thermally conductive features is not physically coupled to thesurface of the semiconductor device.
 16. The power electronics module ofclaim 11, wherein the one or more thermally conductive features arelocated at one or more edges of the surface of the semiconductor device.17. The power electronics module of claim 11, wherein the one or morethermally conductive features comprises a plurality of radially arrangedthermally conductive features.
 18. The power electronics module of claim11, wherein at least one of the one or more thermally conductivefeatures is a sphere that is not physically connected to the surface ofthe semiconductor device.
 19. The power electronics module of claim 11,wherein each electronics device assembly further comprises a jetimpingement nozzle configured to direct the coolant fluid toward thesurface of the semiconductor device.
 20. The power electronics module ofclaim 11, wherein each electronic device assembly further comprises acold plate comprising a heated surface and a cooling surface, whereinthe surface of the semiconductor device is thermally coupled to theheated surface of the cold plate, and the coolant fluid and the phasechange material are thermally coupled to the cooling surface of the coldplate.